operating systems

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OPERATING SYSTEMS BY: Vikhyat Tandon 11thA

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History of computers Hewlett Packard was founded in 1939 by  David Packard and Bill Hewlett, Their first product, the HP 200A Audio Oscillator Walt Disney Pictures ordered eight of the 200B model to use during the creation of the movie “Fantasia.”

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History of computers Computer wars: Germany vs. Britain

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History of computers First generation 1945 - 1955 vacuum tubes, plug boards Still very slow and used for scientific calculations No OS was needed Programs were entered by setting some switches

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History of computers Second generation 1955 – 1965 transistors, batch systems Universities started to buy computers (spending millions of dollars) Punched cards were used To run a job (a program or a set of related programs) first punch it and give the deck to the operators and wait for the output (batch operation) Computers were single user IBM STRETCH DEC PDP-1

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What is an operating System? A program that acts as an intermediary between a user of a computer and the computer hardware. Operating system goals: Execute user programs and make solving user problems easier. Make the computer system convenient to use. Use the computer hardware in an efficient manner. Allows efficient usage; parallel activity, avoids wasted cycles. Provides information protection. Gives each user a slice of the resources. Acts as a control program.

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Features of operating system 1. Program execution. Interrupts Protected mode and supervisor mode. Memory management Virtual Memory Multitasking Disk access and file systems Device drivers Networking Security

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Need of operating system Operating System provides a stable and consistent way to deal with hardware without having to know all the details of the hardware. 2. To manage the hardware and software resources. 3. It plays the role of good parent, making sure that each application gets the necessary resources while playing nicely with other applications.

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Operating System overview The Layers Of A System Humans Program Interface User Programs O.S. Interface O.S. Hardware Interface/ Privileged Instructions Disk/Tape/Memory

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Operating System overview Characteristics Interprets: Interrupt transfers control to the interrupt service routine generally, through the interrupt vector, which contains the addresses of all the service routines. Incoming interrupts are disabled while another interrupt is being processed to prevent a lost interrupt. A trap is a software-generated interrupt caused either by an error or a user request. An operating system is interrupt driven.

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Operating System overview Hardware Support Sequence of events for processing an IO request. Comparing Synchronous and Asynchronous IO Operations

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Operating System overview Hardware Support This is O.S. Bookkeeping. These structures are necessary to keep track of IO in progress.

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Operating System overview Storage Hierarchy Very fast storage is very expensive. So the Operating System manages a hierarchy of storage devices in order to make the best use of resources. In fact, considerable effort goes into this support. Fast and Expensive Slow an Cheap

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Operating System overview Storage Hierarchy Performance

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Operating System overview Storage Hierarchy Caching: Important principle, performed at many levels in a computer (in hardware, operating system, software). Information in use copied from slower to faster storage temporarily. Faster storage (cache) checked first to determine if information is there a. If it is, information used directly from the cache (fast) b. If not, data copied to cache and used there 4. Cache smaller than storage being cached a. Cache management important design problem b. Cache size and replacement policy

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Operating System overview Protection The goal is protecting the Operating System and others from malicious or ignorant users. The User/Supervisor Mode and privileged instructions. Concurrent threads might interfere with others. This leads to protection of resources by user/supervisor mode. These resources include: I/O Define I/O instructions as privileged; they can be executed only in Supervisor mode. System calls get us from user to supervisor mode.

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Operating System overview Protection Memory A user program can only access its own logical memory. For instance, it can't modify supervisor code. Depends on an address translation scheme such as that shown here.

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Operating System overview Protection CPU A clock prevents programs from using all the CPU time. This clock causes an interrupt that causes the operating system to gain control from a user program. For machines connected together, this protection must extend across: Shared resources, Multiprocessor Architectures, Clustered Systems The practice of this is called “distributed operating systems”.

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i/o structure After I/O starts, control returns to user program only upon I/O completion. Wait instruction idles the CPU until the next interrupt Wait loop (contention for memory access). At most one I/O request is outstanding at a time, no simultaneous I/O processing. After I/O starts, control returns to user program without waiting for I/O completion. System call – request to the operating system to allow user to wait for I/O completion. Device-status table contains entry for each I/O device indicating its type, address, and state. Operating system indexes into I/O device table to determine device status and to modify table entry to include interrupt.

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Two i/o method Synchronous Asynchronous

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Various operating systems developed by various companies

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Various operating systems developed by various companies

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Various operating systems developed by various companies

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Previous versions of windows

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Windows xp Windows has had a makeover for XP Updated graphics Clearer Text especially on Flat panel LCD screens (like those on your new systems) Task-oriented interface: Copy, move or delete files and folders conveniently A preview…

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Windows XP Desktop

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Managing Files in Windows XP

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Improved user interface New ways to look at your files and folders More convenient ways of viewing graphics, multimedia Easier to organize your display My Documents and My Computer now Task-oriented A left pane presents tasks varying according to what you select on the right Easier file and folder management

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Familiar features For the user, Windows XP is not a radical break with Windows’ past You can still do almost everything as you used to New possibilities save time Many improvements “under the hood” More stable programming core Based on Windows NT/ Windows 2000 architecture

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Windows 7 overview What is Windows 7 ? Most Recent version of Microsoft Windows Operating system. Windows 7 was released to Manufacturing on July 22,2009,and reached general retail availability on October 22,2009.

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Windows 7 Desktop

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Managing Files in Windows 7

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Benefits of windows 7 Performance : Windows 7 starts, shuts down, and resumes from Standby faster than earlier versions of Windows. Reliability :Reliability improvements in Windows 7 include a Fault Tolerant Heap that resolves common memory management issues. Application Compatibility :A key engineering goal for Microsoft is that software that runs on Windows Vista will run as well or better on Windows 7.

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Device Compatibility : As with software, Microsoft set an engineering goal that devices that work with Windows Vista will also work with Windows 7—and has greatly expanded the list of devices and peripherals that are being tested for compatibility Security : Windows 7 delivers new capabilities to better protect your security and privacy, and makes existing security features such as User Account Control and Windows Defender easier to use. Improved Battery Life : Improvements to power management in Windows 7 will help extend the battery life of your mobile PC.

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Windows 7 requirements

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Features of windows 7 More personal: Redecorate your desktop with fun new themes, slide shows, or handy gadgets. Performance improvements: Designed to sleep and resume quicker, be less memory hungry, and spot USB devices faster. Play To: Play your media on other PCs, stereos, or TVs around the house. Remote Media Streaming: Enjoy music and video on your home PC—even when you\'re not at home. Windows Touch: Pair Windows 7 with a touch screen and you won't always need a keyboard or mouse.

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